Hot-air furnace



(No Model.)

J. EVANS.

HOT AIR FURNACE. No. 471,110. Patented Mar. 2 2, 1892.

. NITED TATES PATENT Prion.

JOHN EVANS, OF PHILADELPHIA, PENNSYLVANIA.

HOT-AIR FURNACE.

SPECIFICATION formingpart of Letters Patent No. 471,110, dated March 22,1892. Application filed June 30,1891. Serial No. 398,082. (No model.)

To all whom it may concern.-

Be'it known that 1, JOHN EVANS, a citizen of the United States, residingat the city of Philadelphia, in the county of Philadelphia and State ofPennsylvania, have invented certain new and useful ImprovementsinHot-Air Furnaces, of which the following is a specification.

My present invention relates to hot-air furnaces in which the cold orincoming air is warmed or heated by passing it through pipes, tubes,conduits, and chambers externally heated in part by radiation from thecombustion-chamber and in part by contact with the escaping products ofcombustion.

The principal objects of my present invention are, first, to reduce thecost of the furnace by simplifying the construction and arrangement ofthe parts thereof; second, to increase the efficiency of the furnace byso arranging the pipes or conduits for conveying the incoming air to thefurnace as that the same are heated for a distance substantially equalto the length of the combustion-chamher; third,to prevent accumulationofsoot and dust from diminishing the efficiency of the heating apparatus,and, fourth, to provide convenient and easy access to the interior ofthe smoke-passage for removing the accumulation of soot and dusttherefrom.

My invention consists of the improvements hereinafter described, andpointed out in the claims.

The nature and characteristic features of the present invention will bemore fully understood from the following description, taken inconnection with the accompanying drawings, forming part hereof, in whichFigure 1 is a section on the line 00 x of Fig. 2, showing theconstruction and arrangement of the parts of a furnace containing orembodying the characteristic features of my invention; and Fig. 2 is ahorizontal section thereof.

In the drawings, a. is an interior cylindrical casing adapted to serveas a combustion-chamber and provided with a grate a and with twoprojections a and a. These projections a and a are provided,respectively, with doors, and serve to permit of the introduction offuel and of the removal of ash, clinker, and other extraneous matter.

I) is an exterior cylindrical casing closed at the top thereof by anair-drumd of the usual construction and at the bottom thereof by asuitable base-plate e, and adapted to serve as the main housing of thefurnace.

c is an annular horizontal partition located near the top of theinterior cylindrical casing a, and serving to divide the interior of thecasing b into a smoke-passage c and an airchamber (1 A portion of theside Walls of the interior casing a is removed, as at a, in 0rder topermit of the escape of the products of combustion from thecombustion-chamber to the smoke-passage c, and the upper portion or hood0 thereof is supported by a flange formed on the upper surface of thepartition b.

c is an offtake pipe for conveying the smoke and gaseous products ofcombustion from the smoke-passage c to the chimney. (Not shown.) Thispipe 0 is provided with lateral branch pipes c and c communicating,respectively, with the smoke-passage 0'. The branch pipe 0 is providedwith a damper c", which when open permits the smoke and other gaseousproducts of combustion to escape from the combustion-chamber directlyinto the offtake-pipe c and hence affords a socalled direct draft. Whenthe damper c is closed, the smoke and other gaseous products ofcombustion pass from the top of the combustion chamber downward throughthe smoke-chamber c and escape through the branch pipe 0 into theofftake-pipe 0 thus forming a so-called indirect draft.

f is an open-top exterior shell or jacket surrounding the housing ormain frame I) of the furnace and mounted on the-base-plate e. The supplyof cold or fresh air is introduced at the open top of this shell orjacket fand descends to the bottom thereof. The supply of air is thenconducted from the bottom of this shell f to the air chamber d by meansof a series of externally-heated pipes or conduits g, located in thesmoke-passage c and disposed around the rear portion of thecombustionchamber, as illustrated in Fig. 2. These pipes g are providedat the lower extremities thereof with elbows g, communicating with thelower portion of the interior of the shell or jacket ft and areconnected with the partition c at the upper extremities. The unionbetween the top of the pipes g and partition 0 may be convenientlyeffected by providing the portion a with annular flanges g and thenfilling the space between the flanges g and pipes g with sand or othersuitable material, so as to form an airtight joint that will afiord thepipes an opportunity to expand and contract without causing the jointsto leak. These pipes g are substantially equal in length to the heightof the combustion-chamber, and therefore are exposed to and heated byall the available heat that is radiated therefrom, it being understoodthat these pipes serve to heat or warm the incoming air. It may beremarked that these pipes or conduits g are preferably located at alittle distancefor example, a half inehfrom the exterior of the casinga, in order to obviate undue heating or drying of the air. The solidmatter carried by the smoke and gaseous products of combustion falls tothe bottom of the smokepassage 0' and collects on the base-plate e andbeneath the elbows g, so that it does not prevent the heat radiated fromthe combustion-chamber from reaching the interior of the incoming airconduits or pipes g.

h and h are doors located in the sidewalls of the extension a of thecasin g a, and h is a door located in the side wall of the casing Z) andbeneath the branch pipe 0", at which pointthe exterior shell f is cutaway, as shown in Fig. 2. These doors 71, h, and 7L2 afford convenientmeans for permitting of the removal of soot or dust from the lowerportion of the smoke-chamber c.

The mode of operation of the hereinabovcdescribed heating appliance isas follows: The damper o is opened and a fire is started on the grate a.The smoke escapes from the casing a, through the space a between thepartition 0 and side walls thereof, into the smoke-passage c, as isindicated by the arrows in Fig. 1, and the smoke escapes from thepassage 0 through the branch pipe 0 into the oitftake 0 as indicated bythe arrow 1 in Fig. 1. After the fire is well started the damper c isclosed and the smoke and heated products of combustion pass downwardaround the pipes g and escape into the otftake 0 through the branch pipe0, as is indicated by the arrow 2 in Fi 1, and the direct radiation fromthe combustion-chamber, as well as the contact of the hot smoke andgases, heat the pipes g. Cold or fresh air is admitted into the shell orjacket fat the open top f thereof, and de scending enters the pipes g,and ascends through the latter into the air-chamber (P, from which it isled off through the hot-air flue (l for use. The course of the airisindicated by the arrow 8 in Fig. 1. It will of course be understood thatthe incoming airis heated by the pipes g, the hood c and also by theheat radiated from the casing b. Moreover, any accumulation of soot ordirt in the smoke-space 0' will collect upon the base-plate e andbeneath the heated portions of the combustion-chamber, and thereforewill not in any way prevent the heating of the pipes g, and

this accumulation of dust or soot may be readily removed by means of thedoors h, h, and IL2 in the manner hereinabove described.

It will be obvious to those skilled in the art to which my inventionappertains that modifications may be made as to minor detailsforinstance, in the location of the doors 7L, h, and h -without departingfrom the spirit of the invention.

Having thus described the nature and ob jeets of my invention, what Iclaim as new, and desire to secure by Letters Patent, is-

1. The combination, in a hot-air furnace, of a main casing closed at thetop by an airdrum provided with an offtake and supported at the bottomon the base-plate, an interior casing forming the wall of thecombustionchamber provided with a grate, a partition located near thetop of the furnace and dividing the space between said casings into asmoke-passage and an air-chamber, the wall of said combustion-chamberbeing partially removed to permit of the escape of the products ofcombustion therefrom to the smokepassage, an open-top jacket surroundingsaid main casing and extending to the base-plate, and a series ofair-inlet pipes or conduits in said smoke-passage in communication withsaid air chamber and jacket, theeonstruction being such that saidair-inlet pipes or conduits are exposed to the available heat ofcombustion the length of said combustionchamber and soot or otherextraneous matter permitted to accumulate at the base of thesmoke-passage, substantially as shown and described.

2. The combiuation,in allot-air furnace, of an exterior metallic housingclosed at the top by an air-drum provided with an offtake and supportedat the bottom on a base-plate, an

open-top jacket surrounding said housing andv supported on saidbase-plate, an interior nietallie casing forming the wall of thecombustion-chamber, with an outlet for the escape of smoke and othergaseous products, a partition near the top of the furnace between theinterior casing and exterior housing, and dividing the space betweensaid casing and housing into an air-chamber and smoke-passage, asmoke-otftake, direct and indirect draft-pipes and connections, a seriesof air inlet pipes or conduits in said smoke-passage and incommunication with said air-chamber and with said open-top j aeket nearthe base of said furnace, the construction being such that the downwardcurrent of air entering at the top of said jacket is heated for adistance sub stantially equal to the length of the furnace, for thepurposes described.

3. The combination, in a hot-air furnace, of a main casing or housingclosed at the top by an air-drum having an oiiftake and at the bottomsupported on a solid base-plate, an interior casing forming the wall ofa combustion-chamber provided with a grate and two projections closed byremovable doors for admitting fuel above said grate and removingextraneous matter from the bottom of said furnace, a partition near thetop of the furnace dividing the space between said housing and easinginto an air-chamber and a smokepassage, direct and indirect draftconnections, a smoke offtake, an open top jacket surrounding said maincasing and supported on said base-plate, and a series of pipes locatedin said smoke-passage and in communication with said air-chamber andwith said jacket near the base of the furnace, substantially as shown,and for the purposes described.

4. The combination, in a hot-air furnace, of a main housing closed atthe top by an airdrum provided with an offtake and at the bottomsupported on a solid base-plate, an interior casing forming the wall ofa combustionchamber having a grate mounted therein and projections orextensions closed by removable doors to permit of the supply of fuel tothefurnace above said grate and to permit of the removal of extraneousmatter from the furnace at or near the bottom thereof, a partition nearthe top of the furnace dividing the space between said housing andcasing into an air-chamber and a smoke-passage, an open-top jacketsurrounding said housing, in-

coming air-pipes extending nearly to the bottom of said smoke-passage, aseries of doors located at the base of the wall of said passage toafford access to the interior of the smoke passage beneath said incomingair-pipes, and

- a smoke-offtake, substantially as shown, and

for the purposes described.

5. The combination, in a hot-air furnace, of a main casing closed at thetop by an airdrum provided with an offtake and supported on thebase-plate of the furnace and surrounded with an open-top jacket, asmokeoiftake, direct and indirect draft connections, an interior casingforming the wall of a combustion-chamber provided with projectionshaving doors adapted to permit of fuel being admitted and of extraneousmatter being removed from the furnace, a partition dividing the spacebetween said casings into an airchamber and smoke-passage, a series ofincoming pipes located in said passage, the construction being such thatsaid pipes are heated for a distance equal to the height of thecombustion-chamber, and the currents of air conducted downward betweensaid jacket and main casing heated in its upward passage between thewalls of the combustion-chamber and main casing to said hot-air drum,substantially as shown, and for the purposes described. 1

6. A hot-air furnace provided with a main casing closed by an air-drumprovided with an offtake and supported on a solid baseplate, acentrally-located combustion chamber, a smoke-passage surrounding thesame, a series of incoming air-pipes located in said passage, asmoke-olftake, direct and indirect draft connections, an open-top jacketsurrounding the main casing, and the incoming air-extendin g in adownward direction to near the bottom of said furnace and heated in anupward direction in said pipes between said main casing and chamber, forthe purposes described.

7. The combination, in a hot-air furnace, of the base-plate e, thecasings a and b, the extension a smoke-chamber c, the doors h and h inthe walls of said extension, and the door k in the wall of said casing12, all arranged,

substantially as described, to permit of the removal of soot or dustfrom the lower part of said smoke-chamber.

In witness whereof I have hereunto set my signature in the presence oftwo subscribing witnesses.

JOHN EVANS. Witnesses:

THOMAS M. SMITH, RICHARD O. MAXWELL.

